by Jim Michaels, USA TODAY

by Jim Michaels, USA TODAY

WASHINGTON ‚?? NATO's military leadership is scrambling to assure jittery Central European nations that the alliance will be able to defend them if Russian-sponsored violence in Ukraine spills outside its borders and threatens member nations.

Gen. Philip Breedlove, the top military commander of the NATO alliance, has presented a number of options to NATO's political leadership, which is likely to discuss them at a meeting Wednesday.

The plan is an effort to provide assurances for NATO members, such as Poland and the Baltic states, that the United States and its allies will be able to protect countries within the alliance.

"They are looking for reassurance," said Steven Pifer, a former ambassador to Ukraine.

NATO and the United States have already beefed up their naval presence in the Black Sea and increased air patrols over the Baltic nations.

Poland and the Baltic states - Latvia, Estonia and Lithuania - may want the addition of ground troops to help protect their countries from Russian aggression, Pifer said.

"What they would really like to have is some NATO military presence on the ground," Pifer said.

The United States would be a key part of any move to bolster NATO defenses, but the Pentagon's strategy of "pivoting" toward Asia and drawing down forces in Europe has left the military with fewer troops and equipment there.

There are about 67,000 U.S. troops in Europe, according to U.S. European Command. That's down from 100,000 just several years ago.

Analysts say it is unlikely the United States would take any military action as long as the crisis is contained to Ukraine, which is not a member of NATO. Any attack on a NATO member country, however, requires a response from the alliance under the terms of membership.

The Obama administration said it is sticking with its policy of applying diplomatic and economic pressure on Russia and providing non-lethal aid to Ukraine's military. It has also said it does not see a military solution to the crisis.

The White House is considering additional economic sanctions against Russia that could be announced as early as this week. "We are actively looking at our options," Press Secretary Jay Carney said Tuesday.

State Department spokeswoman Jen Psaki said Tuesday, "Our national security team is in active discussions about the next round of sanctions, as they have been. The secretary also spent this morning on a range of phone calls, including with Foreign Minister Fabius, EU High Representative (Catherine) Ashton, German Foreign Minister (Frank-Walter) Steinmeier, and UK Foreign Secretary (William) Hague, because obviously coordination with the Europeans and taking complementary steps is a priority. So not only do we anticipate additional sanctions at some point, we're preparing additional steps."

Ukraine's government has requested a range of military supplies from the United States, which remains under review, but the Pentagon said the current focus remains on supplying Ukraine with non-lethal aid, such as food rations.

The Pentagon has also been involved in general consultations with counterparts in Ukraine.

It has amassed thousands of troops along the border of eastern Ukraine, raising fears Russian leader Vladimir Putin will use the pretext of the pro-Russian demonstrations to repeat events in Crimea, where Russian troops invaded to "protect" ethnic Russians.

That set conditions for a referendum to break the region away from Ukraine and bring it under Russian authority.

Ukraine's government this week launched an "anti-terrorist" operation in parts of eastern Ukraine where pro-Russian demonstrators have taken over government buildings and other installations.

On Tuesday, government troops clashed with pro-Russian demonstrators at a small airport in eastern Ukraine.

The operation comes in the wake of a request from Ukraine's acting president, Oleksandr Turchynov, to the United Nations to send peacekeepers to his embattled country. That is not likely to happen since Russia has a veto on the U.N. Security Council.